Excercise has long been thought to be beneficial to diabetic patients but has not been studied with regard to the special problems involved in managing diabetis in pregnant women. Thus, the effect(s) of excercise on the quantitative aspects of the management of Type I (insulin-deficient, IDDM) Type II (non-insuliun-dependent NIDDM) and gestational (GDM) diabetes will be investigated in sequential fashion throughout pregnancy and post partum period. The effectiveness of a prescribed program of a graded and measured amount of moderate walking excercise will be compared with the usual and customary non-specific instructions for excercise during pregnancy. Quantitative indices of improvement in carbohydrate and fat metabolism will be assessed by longitudinal observations of changes in plasma glucose, mean amplitude of glucemic excursions (MAGE), insulin, C-peptide, glucagon and lipids in response to prescribed meals throughout the 24th day and to a 400 kcal mixed meal tolerance test (MTT). In addition, insulin requirements and HbA1c concentrations will be compared among groups. The effect of maternal excercise on the fetus and neonate will also be assessed. These investigations will test the efficacy of a prescribed regimen of walking as a simple, inexpensive therapeutic adjunct to the treatment of diabetes in pregnant women.